Engine starter gearing



March 1955 G. s. SPENCER ENGINE STARTER GEARING Filed Dec. 18, 1953 5; 3m: l'l l m l 1 6 J1 k Li a 5||\1\\H 6 M @wl ,6 1

INVENTOR.

WITNESS:

United States Patent ENGINE STARTER GEARIN G Glenn S. Spencer,Horseheads, N. Y., assignor to Bendix Aviation Corporation, ElmiraHeights, N. Y., a corporation of Delaware Application December 18, 1953,Serial No. 399,067 4 Claims. (Cl. 74-7) The present invention relates toengine starter gearing and more particularly to that type in whichengagement is brought about by automatic traversal of a control not on arotating screw shaft.

In drives of this type, one of the problems which is always present isthe prevention of pinion drift due to engine vibration. When the engineis running there IS always a certain amount of vibration due to theoscillation and reciprocation of its parts, and since the starting motoris usually mounted on the engine frame, it necessarily is subject to thesame vibration.

It often happens that at certain engine speeds this vibration causes thestarter drive pinion to move away from its idle position on the screwshaft and come into engagement with the ring gear of the engine, and ifsuch engagement occurs frequently, attrition of the ends of the pinionand gear teeth may occur.

The exact method by which this undesired traversal or drift is broughtabout is somewhat obscure, but the forces involved are in some instancesvery substantial.

Most cases of pinion drift have been cured by the use of detents,compression springs and counterweights on the pinion, or by combinationsof such devices, but in some installations it has been found to be quitedifficult to prevent the pinion from drifting at certain critical enginespeeds.

It is an object of the present invention to provide an engine starterdrive involving a novel approach to the problem of pinion drift.

It is another object to provide such a device in which vibration of theparts is caused to exert a force tending to move the pinion on the screwshaft in the direction away from the engine gear.

Further objects and advantages will be apparent from the followingdescription taken in connection with the accompanying drawing in which:

Fig. 1 is a side elevation partly broken away and in section of astarter drive incorporating a preferred embodiment of the invention;

Fig. 2 is a section on an enlarged scale taken substantially on the line2-2 of Fig. 1;

Fig. 3 is an enlarged detail of a portion of the control nut showing theanti-drift spring thimble mounted thereon; and

Fig. 4 is an elevation of the stock from which the antidrift thimble isformed.

In Fig. 1 of the drawing there is illustrated a starter drive of thetype disclosed in the patent to Buxton 2,609,695 issued September 9,1952. As there shown a power shaft 1 has a hollow sleeve 2 fixedlymounted thereon, and a screw shaft 3 is slidably journalled on thesleeve 2 between a stop collar 4 and a clutch member 5 which is drivenfrom the sleeve 2 by means of a spring connection 6, and which has anoverrunning clutch connection 7 with the screw shaft.

A pinion 8 is slidably journalled on the power shaft 1 for movement intoand out of mesh with an engine gear 9, and a control nut 11 threaded onthe screw shaft 3 is connected to the pinion 8 by means of a barrelmember 12.

Patented Mar. 22, 1955 Fee According to the present invention a thimble13 is rigidly mounted on the control nut and has a plurality of elasticarms 14 which are bent inwardly and bear fric tionally at their ends onthe surface of the screw shaft 3. The inclination of the arms isopposite to the direction of rotation of the power shaft as indicated bythe arrow (11) whereby relative lateral movement or vibration of thecontrol nut on the screw shaft sets up an action analogous to a pawl andratchet, which tends to rotate the control nut on the screw shaft in thedirection of drive, that is the direction of rotation of the power shaft1.

The thimble 13 is retained on the control nut by means of a rim 15 whichis pressed into a groove 16 in the control nut as shown in Fig. 3. Theangular position of the thimble on the control nut is determined bymeans of a notch 17 in the control nut which receives the inturned end18 of the sheet metal strip from which the thimble is formed. By thismeans the ends of the arms 14 are uniformly positioned with respect tothe threads of the screw shaft and nut. Fig. 4 shows the strip of sheetmetal 19 from which the thimble 13 is formed. In the formation of thethimble the arms 14 are punched inwardly and formed as illustrated inFig. 2, the end 18 is bent inwardly at right angles, and the strip isrolled up so as to elastically clasp the control nut 11 and hold the rim15 and end 18 properly seated in the nut.

In operation, when the power shaft 1 is rotated in the direction of thearrow, the consequent rotation of the screw shaft traverses the controlnut and consequently moves the pinion 8 into mesh with the engine gear9. During this time the arms 14 tend to cause rotation of the controlnut with the screw shaft but do not have sufficient frictional driveeffect to interfere with the meshing operation.

When the engine starts, the pinion is returned to its idle position asdetermined by the control nut engaging the ends of the threads on thescrew shaft. Thereafter, the spring arms 14 convert any relativevibration between the screw shaft and pinion into a force tending torotate the control nut on the screw shaft in the direction of rotationof the power shaft, and consequently to hold the control nut in its idleposition.

Although but one form of the invention has been shown and described indetail it will be understood that changes may be made in the design andarrangement of the parts without departing from the spirit of theinvention.

I claim:

1. In an engine starter drive a power shaft, a pinion movable thereoninto and out of mesh with a gear on the engine to be started, a screwshaft, means for rotating the screw shaft from the power shaft, acontrol nut on the screw shaft, means connecting the control nut to thepinion, and means responsive to relative vibration of the screw shaftand control nut for rotating the control nut relative to the screw shaftin the direction to demesh the pinion.

2. An engine starter drive as set forth in claim 1 in which the meansfor rotating the control nut constitutes a frictional drivingconnection.

3. An engine starter drive as set forth in claim 2 in which thefrictional driving connection between the screw shaft and control nutcomprises a member fixedly mounted on one of said elements, having aspring arm bearing on the other element, said arm being inclined in sucha direction that relative lateral movement of the elements causes thedesired relative rotation.

4. An engine starter drive as set forth in claim 2 in which saidfrictional driving connection comprises a thimble fixed on the controlnut having an elastic arm which is bent inwardly at an inclinationopposite to the direction of rotation of the drive and bearsfrictionally on the surface of the screw shaft.

No references cited.

